Hi Jan, It's not clear to me why in Section 3.1.5, a global /64 prefix is recommended for PPPoE connections.
Sections 3.1.2 and 3.1.3 talk about directly connecting hosts without any kind of CPE. As far I know, the last time that was in fashion for PPP links was with dial-up. So I think that for PPPoE we can safely assume that a CPE can request a prefix using DHCPv6 PD. As indirectly mentioned in Section 3.1.2, assigning a global /64 to a point-to-point link may open certain kinds of attacks. All links with a global /64 risk a ND exhaustion attack. However, point-to-points also risk a ping-pong attack. For a PPPoE link these issues are trivially solved to leaving the link unnumbered.
